asp.net mvc 4 - user isn't authenticated in custom authorize attribute -

i've made own authorize attribute, , looks like

public class redirectauthorize : authorizeattribute {     protected override void handleunauthorizedrequest(authorizationcontext filtercontext)     {         if (!filtercontext.httpcontext.user.identity.isauthenticated)         {             filtercontext.result = new redirecttorouteresult(new             routevaluedictionary(new { controller = "notexist" }));                     }     } } 

so if user isn't authenticated, want them redirected notexist controller. i've debugged , seems unauthorized users in if clause, correct. i've tried doing logged in users, , in if clause wrong.

i dont understand why happening. makes me hesitate whether log-in didnt work. right way of logging user in?

formsauthentication.setauthcookie(acc.username, false); 

i've never made log-in system in asp.net mvc before, please tell me i'm doing wrong.

edit:

it seems default [authorized] attribute isn't working either... think problem lays in log in:

[httppost] public actionresult login(user acc) {     if(modelstate.isvalid)     {         if (validate(acc.username, acc.password))         {             formsauthentication.setauthcookie(acc.username, false);             return redirecttoaction("index", "system");         }     }      modelstate.addmodelerror("incorrectdetails", "wrong details. please try again.");     return view(acc);  } 

the custom authorize attribute looks correct.

since setting cookie guess not using built-in membership provider.

if set cookie yourself, need read auth cookie , set identity , principal objects on each request. otherwise, httpcontext.user.identity.isauthenticated false, seems experiencing.